11.3 Episiotomy: Clinical Indications, Infiltration Technique & Incision Anatomy

Episiotomy: Clinical Indications, Infiltration Technique & Incision Anatomy

Perineal trauma is one of the most common complications of vaginal childbirth, affecting up to 85% of women delivering vaginally in the United Kingdom. An episiotomy is a deliberate, surgically executed incision of the perineum and posterior vaginal wall performed during the crowning of the fetal head to enlarge the vaginal introitus. Historically viewed as a routine preventative procedure, modern evidence-based midwifery practice strictly reserves episiotomy for specific, justified clinical scenarios. A comprehensive grasp of perineal surgical anatomy, local anaesthetic pharmacology, safe operative technique, and structured perineal repair is an essential competency assessed in the NMC Midwifery Test of Competence.

---

The Restrictive Episiotomy Policy: Evidence & Guidelines

For much of the twentieth century, routine episiotomy was widely advocated under the unsubstantiated premise that a clean surgical incision healed better than a spontaneous laceration, preserved pelvic floor muscle integrity, and prevented future urinary or faecal incontinence. Extensive contemporary research, including comprehensive Cochrane systematic reviews and the landmark findings underpinning NICE guideline NG235 (Intrapartum care) and RCOG Green-top Guideline No. 29, has completely dismantled these assumptions.

Clinical Evidence Against Routine Episiotomy

Rigorous comparative trials demonstrate that routine episiotomy:

• Increases Overall Perineal Trauma: Substantially higher rates of severe posterior perineal lacerations, extensive tissue disruption, and blood loss.
• Impairs Maternal Recovery: Significantly elevated postpartum perineal pain, increased requirements for analgesia, delayed ambulation, and higher incidences of wound infection and breakdown.
• Elevates Dyspareunia: Prolonged postpartum superficial and deep dyspareunia (painful intercourse) lasting beyond 3 to 6 months.
• Fails to Prevent Incontinence: Provides no protective benefit against long-term urinary incontinence, pelvic organ prolapse, or faecal incontinence.

Consequently, UK national clinical practice enforces a restrictive episiotomy policy. Midwives must never perform an episiotomy routinely or on the sole basis of parity (e.g., being nulliparous).

---

Evidence-Based Clinical Indications for Episiotomy

Under NICE guidelines and RCOG standards, an episiotomy is clinically indicated only when there is a specific, compelling clinical rationale:

1. Suspected Acute Fetal Compromise: During the second stage of labour, when pathological fetal heart rate patterns (such as prolonged fetal bradycardia <100 bpm, severe late decelerations, or acute failure to recover) indicate imminent hypoxia. An episiotomy enlarges the soft tissue outlet, shortening the second stage by several vital minutes to expedite birth.
2. Instrumental Vaginal Delivery (Operative Vaginal Birth): When birth requires the application of obstetric forceps or a ventouse (vacuum extractor). In nulliparous women undergoing instrumental vaginal delivery, a well-angled mediolateral episiotomy significantly reduces the incidence of Obstetric Anal Sphincter Injuries (OASIS)—third- and fourth-degree perineal tears.
3. Shoulder Dystocia: When the fetal anterior shoulder becomes impacted behind the maternal pubic symphysis.

---

Informed Consent & Maternal Communication

Performing an episiotomy without maternal consent constitutes a legal battery and a grave violation of The Code. Even in urgent clinical emergencies, the midwife must communicate clearly with the woman:

• Explain the clinical indication (e.g., the baby's heart rate has dropped and birth must be expedited).
• Describe what the procedure involves and why local anaesthetic is being administered.
• Explicitly state the potential risks (bleeding, perineal pain, infection, extension of the tear) and immediate benefits.
• Obtain clear, verbal consent. If a woman with mental capacity declines, her refusal must be respected, and alternative strategies (e.g., maternal position change, continuous perineal support) instituted.

---

Local Anaesthetic Infiltration: Pharmacology & Technique

Except in catastrophic situations where the perineum is profoundly stretched, ischaemic, and birth is occurring instantaneously during acute resuscitation, an episiotomy must never be performed without effective analgesia.

Pharmacological Choice & Safe Dosing

• Agent of Choice: 1% Lidocaine Hydrochloride (Lignocaine) plain (without adrenaline/epinephrine).
• Mechanism of Action: Blocks voltage-gated sodium channels along the nerve axons of the pudendal nerve branches, preventing action potential generation and transmission of pain signals.
• Recommended Volume: 10 mL to 20 mL of 1% lidocaine.
• Maximum Safe Dose: Plain lidocaine has a maximum safe threshold of 3 mg/kg of maternal body weight (up to approximately 200 mg, which equates to 20 mL of a 1% solution [10 mg/mL] in an average 70 kg woman).

Step-by-Step Infiltration Technique

┌─────────────────────────────────────────────────────────────────┐
│                     STEP 1: FETAL PROTECTION                    │
│ Insert index & middle fingers of non-dominant hand into vagina  │
│ between the presenting fetal head and the posterior perineum    │
└────────────────────────────────┬────────────────────────────────┘
                                 │
                                 ▼
┌─────────────────────────────────────────────────────────────────┐
│                     STEP 2: NEEDLE INSERTION                    │
│ Introduce 21G/23G green/blue needle at posterior fourchette     │
│ in the midline, directing towards the right ischial tuberosity  │
└────────────────────────────────┬────────────────────────────────┘
                                 │
                                 ▼
┌─────────────────────────────────────────────────────────────────┐
│               STEP 3: MANDATORY ASPIRATION CHECK                │
│ Pull back syringe plunger. Verify NO blood returns into barrel. │
│ Prevents accidental entry into internal pudendal vessels.       │
└────────────────────────────────┬────────────────────────────────┘
                                 │
                                 ▼
┌─────────────────────────────────────────────────────────────────┐
│                 STEP 4: FAN-SHAPED INFILTRATION                 │
│ Slowly inject lidocaine while continuously withdrawing needle.  │
│ Infiltrate perineal skin, subcutaneous fat, and muscle layer.   │
└────────────────────────────────┬────────────────────────────────┘
                                 │
                                 ▼
┌─────────────────────────────────────────────────────────────────┐
│                 STEP 5: ANALGESIC LATENCY CHECK                 │
│ Allow 2 to 3 minutes for full nerve blockade. Test sensation    │
│ gently with toothed forceps prior to performing incision.       │
└─────────────────────────────────────────────────────────────────┘

---

Surgical Anatomy of the Right Mediolateral Episiotomy

In the United Kingdom, NICE NG235 and RCOG guidance recommend a mediolateral episiotomy, usually on the right side, angled at 45 to 60 degrees from the vertical when the perineum is distended; this is the Right Mediolateral Episiotomy.

Anatomical Landmarks and Trajectory

1. Point of Origin: Begins in the vertical midline at the posterior fourchette of the vaginal introitus.
2. Incision Trajectory: Directed diagonally downwards and outwards towards the maternal right ischial tuberosity.
3. Incision Angle: The incision must be angled at 45 to 60 degrees relative to the vertical sagittal midline when the perineum is fully distended and crowning.

When the fetal head delivers and the perineum recoils, an incision made at 60 degrees during crowning naturally relaxes to an angle of approximately 45 degrees. Incisions cut at angles less than 45 degrees significantly increase the danger of tearing directly into the anal sphincter.

Anatomical Musculature and Structures Transected

A correctly performed mediolateral episiotomy deliberately incises the following anatomical layers:

1. Vaginal Epithelium and posterior submucosal tissue.
2. Perineal Skin and underlying subcutaneous adipose tissue.
3. Bulbocavernosus Muscle (bulbospongiosus): Surrounds the vaginal orifice and contributes to the anterior perineal body.
4. Superficial Transverse Perineal Muscle: Runs transversely from the ischial tuberosity to the central perineal tendon.
5. Deep Perineal Musculature: Medial fibres of the pubococcygeus muscle (part of the levator ani complex) and connective tissue of the central perineal body.

Importantly, a correctly executed mediolateral episiotomy carefully spares the external anal sphincter (EAS), the internal anal sphincter (IAS), and the anal canal mucosa.

Timing and Execution of the Incision

• Optimal Timing: The incision must be performed at crowning, when approximately 4 to 5 cm of the fetal presenting part is visible at the introitus during a contraction.
  • Cutting too early (before crowning) results in excessive, uncontrolled haemorrhage from untensioned vascular beds and fails to accelerate delivery.
  • Cutting too late (when the perineum is already overstretched and tearing) fails to prevent extensive spontaneous lacerations.
• Instrument Handling: Use specialized, blunted episiotomy scissors (such as Mayo or Braun-Stadler scissors). The midwife places the index and middle fingers of the non-dominant hand inside the vagina, depressing the perineal tissues to protect the fetal scalp. The scissors are inserted with the blade open, angled firmly at 45 to 60 degrees, and a single, deliberate 3 to 5 cm snip is executed during the peak of the contraction.

---

Perineal Repair Technique, Haemostasis & Aftercare

Following the birth of the baby and completion of the third stage of labour, the midwife must systematically inspect the genital tract to classify the extent of trauma and execute a meticulous surgical repair.

Pre-Repair Assessment & Digital Rectal Examination (DRE)

• Ensure optimal visualization with an adjustable direct examination light.
• Provide adequate analgesia (e.g., top-up local lidocaine infiltration, pudendal block, or epidural top-up).
• Mandatory Digital Rectal Examination (DRE): Before commencing any suturing, the midwife must perform a digital rectal examination to verify the integrity of the anorectal sphincter complex. This step is essential to rule out an unrecognized third-degree tear (involving the external/internal anal sphincter) or fourth-degree tear (involving the anal epithelium).

The Three-Layer Surgical Closure Technique

Perineal repair should be performed using an absorbable synthetic braided suture material, such as polyglactin 910 (Vicryl Rapide), utilizing a continuous suturing technique, which evidence demonstrates causes less postpartum pain than interrupted sutures:

1. Layer 1: Vaginal Trauma & Apex Closure: Place the initial anchoring suture approximately 1 cm above the apex of the vaginal laceration to securely ligate retracted bleeding vessels. Continue with a continuous, non-locking suture along the vaginal epithelium down to the level of the hymenal ring.
2. Layer 2: Perineal Muscle Reconstruction: Re-approximate the transected muscle bodies (bulbocavernosus and superficial transverse perineal muscles) using continuous or interrupted sutures. Ensure complete closure of dead space to prevent the formation of a concealed, painful perineal haematoma.
3. Layer 3: Skin Re-approximation: Close the perineal skin using a continuous subcuticular suture placed within the dermal layer. Subcuticular skin closure eliminates transcutaneous suture entry wounds, substantially reducing postoperative oedema, suture tightness, and superficial wound pain.

Post-Procedure Verification & Aftercare

• Repeat Digital Rectal Examination: Following completion of the repair, a second DRE must be performed to confirm that no sutures have inadvertently breached the rectal mucosa (which could cause a rectovaginal fistula) and to verify normal anal sphincter tone.
• Swab and Needle Count: Perform a formal, recorded count of all swabs, needles, and instruments with a second practitioner to ensure no foreign bodies remain retained within the vagina.
• Postnatal Hygiene and Analgesia: Prescribe multimodal analgesia (paracetamol combined with NSAIDs such as ibuprofen, unless contraindicated). Educate the woman regarding local hygiene (frequent sanitary towel changes, daily showering, warm water rinses), pelvic floor muscle exercises to restore tone, and red flag symptoms of wound infection or dehiscence (foul-smelling lochia, worsening unremitting throbbing pain, pyrexia).